path: root/arch/powerpc/kernel/module_64.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*  Kernel module help for PPC64.
    Copyright (C) 2001, 2003 Rusty Russell IBM Corporation.

*/

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/elf.h>
#include <linux/moduleloader.h>
#include <linux/err.h>
#include <linux/vmalloc.h>
#include <linux/ftrace.h>
#include <linux/bug.h>
#include <linux/uaccess.h>
#include <linux/kernel.h>
#include <asm/module.h>
#include <asm/firmware.h>
#include <asm/code-patching.h>
#include <linux/sort.h>
#include <asm/setup.h>
#include <asm/sections.h>
#include <asm/inst.h>

/* FIXME: We don't do .init separately.  To do this, we'd need to have
   a separate r2 value in the init and core section, and stub between
   them, too.

   Using a magic allocator which places modules within 32MB solves
   this, and makes other things simpler.  Anton?
   --RR.  */

bool module_elf_check_arch(Elf_Ehdr *hdr)
{
	unsigned long abi_level = hdr->e_flags & 0x3;

	if (IS_ENABLED(CONFIG_PPC64_ELF_ABI_V2))
		return abi_level == 2;
	else
		return abi_level < 2;
}

#ifdef CONFIG_PPC64_ELF_ABI_V2

static func_desc_t func_desc(unsigned long addr)
{
	func_desc_t desc = {
		.addr = addr,
	};

	return desc;
}

/* PowerPC64 specific values for the Elf64_Sym st_other field.  */
#define STO_PPC64_LOCAL_BIT	5
#define STO_PPC64_LOCAL_MASK	(7 << STO_PPC64_LOCAL_BIT)
#define PPC64_LOCAL_ENTRY_OFFSET(other)					\
 (((1 << (((other) & STO_PPC64_LOCAL_MASK) >> STO_PPC64_LOCAL_BIT)) >> 2) << 2)

static unsigned int local_entry_offset(const Elf64_Sym *sym)
{
	/* sym->st_other indicates offset to local entry point
	 * (otherwise it will assume r12 is the address of the start
	 * of function and try to derive r2 from it). */
	return PPC64_LOCAL_ENTRY_OFFSET(sym->st_other);
}
#else

static func_desc_t func_desc(unsigned long addr)
{
	return *(struct func_desc *)addr;
}
static unsigned int local_entry_offset(const Elf64_Sym *sym)
{
	return 0;
}

void *dereference_module_function_descriptor(struct module *mod, void *ptr)
{
	if (ptr < (void *)mod->arch.start_opd ||
			ptr >= (void *)mod->arch.end_opd)
		return ptr;

	return dereference_function_descriptor(ptr);
}
#endif

static unsigned long func_addr(unsigned long addr)
{
	return func_desc(addr).addr;
}

static unsigned long stub_func_addr(func_desc_t func)
{
	return func.addr;
}

#define STUB_MAGIC 0x73747562 /* stub */

/* Like PPC32, we need little trampolines to do > 24-bit jumps (into
   the kernel itself).  But on PPC64, these need to be used for every
   jump, actually, to reset r2 (TOC+0x8000). */
struct ppc64_stub_entry {
	/*
	 * 28 byte jump instruction sequence (7 instructions) that can
	 * hold ppc64_stub_insns or stub_insns. Must be 8-byte aligned
	 * with PCREL kernels that use prefix instructions in the stub.
	 */
	u32 jump[7];
	/* Used by ftrace to identify stubs */
	u32 magic;
	/* Data for the above code */
	func_desc_t funcdata;
} __aligned(8);

struct ppc64_got_entry {
	u64 addr;
};

/*
 * PPC64 uses 24 bit jumps, but we need to jump into other modules or
 * the kernel which may be further.  So we jump to a stub.
 *
 * Target address and TOC are loaded from function descriptor in the
 * ppc64_stub_entry.
 *
 * r12 is used to generate the target address, which is required for the
 * ELFv2 global entry point calling convention.
 *
 * TOC handling:
 * - PCREL does not have a TOC.
 * - ELFv2 non-PCREL just has to save r2, the callee is responsible for
 *   setting its own TOC pointer at the global entry address.
 * - ELFv1 must load the new TOC pointer from the function descriptor.
 */
static u32 ppc64_stub_insns[] = {
#ifdef CONFIG_PPC_KERNEL_PCREL
	/* pld r12,addr */
	PPC_PREFIX_8LS | __PPC_PRFX_R(1),
	PPC_INST_PLD | ___PPC_RT(_R12),
#else
	PPC_RAW_ADDIS(_R11, _R2, 0),
	PPC_RAW_ADDI(_R11, _R11, 0),
	/* Save current r2 value in magic place on the stack. */
	PPC_RAW_STD(_R2, _R1, R2_STACK_OFFSET),
	PPC_RAW_LD(_R12, _R11, 32),
#ifdef CONFIG_PPC64_ELF_ABI_V1
	/* Set up new r2 from function descriptor */
	PPC_RAW_LD(_R2, _R11, 40),
#endif
#endif
	PPC_RAW_MTCTR(_R12),
	PPC_RAW_BCTR(),
};

/*
 * Count how many different r_type relocations (different symbol,
 * different addend).
 */
static unsigned int count_relocs(const Elf64_Rela *rela, unsigned int num,
				 unsigned long r_type)
{
	unsigned int i, r_info, r_addend, _count_relocs;

	/* FIXME: Only count external ones --RR */
	_count_relocs = 0;
	r_info = 0;
	r_addend = 0;
	for (i = 0; i < num; i++)
		/* Only count r_type relocs, others don't need stubs */
		if (ELF64_R_TYPE(rela[i].r_info) == r_type &&
		    (r_info != ELF64_R_SYM(rela[i].r_info) ||
		     r_addend != rela[i].r_addend)) {
			_count_relocs++;
			r_info = ELF64_R_SYM(rela[i].r_info);
			r_addend = rela[i].r_addend;
		}

	return _count_relocs;
}

static int relacmp(const void *_x, const void *_y)
{
	const Elf64_Rela *x, *y;

	y = (Elf64_Rela *)_x;
	x = (Elf64_Rela *)_y;

	/* Compare the entire r_info (as opposed to ELF64_R_SYM(r_info) only) to
	 * make the comparison cheaper/faster. It won't affect the sorting or
	 * the counting algorithms' performance
	 */
	if (x->r_info < y->r_info)
		return -1;
	else if (x->r_info > y->r_info)
		return 1;
	else if (x->r_addend < y->r_addend)